DESCRIPTION: [unreadable] Epidemiological studies of US nuclear weapons workers allow evaluation of the effects of low dose, low dose rate radiation exposures accrued in an environment of mixed radiological and non-radiological exposures associated with the USDOE weapons complex. In the proposed study, we will examine a cohort of nearly 22,000 badge-monitored workers at the Savannah River Site (SRS) who will be followed over a fifty-year period. Past research on this [unreadable] epidemiologically important population has focused on analyses of standardized mortality ratios. The proposed study, in contrast, will focus on radiation-mortality associations in this cohort while investigating potential sources of bias and effect modification. We will examine [unreadable] radiation-mortality associations under varying lag assumptions, and investigate potential changes with age-at-exposure in susceptibility to the carcinogenic effects of radiation. Next, we will investigate differences between workers in the carcinogenic effects of radiation exposure due to non-radiological exposures accrued at SRS. Mechanistic models of carcinogenesis suggest that initiating exposure to some non-radiological carcinogens may modify the effects of subsequent ionizing radiation exposures. We will use a job-exposure matrix to identify workers with routine potential for exposure to several non-radiological agents, and apply innovative methods to examine the joint effects of radiological and non-radiological exposures. Finally, we will examine the role of tritium and neutron exposures in these analyses of radiation-mortality associations. We will investigate whether variation in radiation risk estimates between [unreadable] subgroups of workers reflects heterogeneity in radiological exposures. Study results for this large USDOE cohort will be evaluated in relation to observations from studies of other DOE facilities; and, study data will be compiled in a manner that will facilitate future pooled analyses. In this way, the proposed work will substantially strengthen the available epidemiological information about low level radiation effects in USDOE cohorts. [unreadable] [unreadable]